Japanese Patent Application Publication No. 2011-90823 (Patent Literature 1) describes fuel cells vehicle provided with a boost converter which boosts an output voltage of a fuel cell. Low voltage terminals of the boost converter are connected to the fuel cells, and high voltage terminals thereof are connected to an inverter. The inverter converts boosted DC power to AC power suitable for driving an electric traction motor. In general, the boost converter has a current smoothing capacitor connected between a positive terminal and a negative terminal of the high voltage terminals. When the fuel cells are stopped, the capacitor retains a voltage higher than the output voltage of the fuel cells. The fuel cells also retain a corresponding voltage for a while after having stopped.
In the fuel cell vehicle of Patent Literature 1, when a main switch of the vehicle is turned off, the fuel cells and the capacitor are discharged according to the following procedure. Firstly, an oxygen supplier is stopped but a pump is not stopped, and a fuel supply is continued for a while. This fuel supply enables electricity generation to continue until remaining oxygen is consumed. In the fuel cell vehicle of Patent Literature 1, the pump is stopped after the remaining oxygen has been consumed. Next, the boost converter is activated, and remaining charges in the fuel cells are discharged to a high voltage side of the boost converter. The boost converter is stopped after the remaining charges in the fuel cells have been discharged. Then, the inverter is operated to discharge the capacitor through the inverter.